Function GetSourceSampleOffset

3rdparty/openal/al/source.cpp:179–218

GetSourceSampleOffset * * Gets the current read offset for the given Source, in 32.32 fixed-point * samples. The offset is relative to the start of the queue (not the start of * the current buffer). */

 * the current buffer).
 */
int64_t GetSourceSampleOffset(ALsource *Source, ALCcontext *context, nanoseconds *clocktime)
{
    ALCdevice *device{context->mDevice.get()};
    const ALbufferlistitem *Current;
    uint64_t readPos;
    ALuint refcount;
    ALvoice *voice;

    do {
        Current = nullptr;
        readPos = 0;
        while(((refcount=device->MixCount.load(std::memory_order_acquire))&1))
            std::this_thread::yield();
        *clocktime = GetDeviceClockTime(device);

        voice = GetSourceVoice(Source, context);
        if(voice)
        {
            Current = voice->mCurrentBuffer.load(std::memory_order_relaxed);

            readPos  = uint64_t{voice->mPosition.load(std::memory_order_relaxed)} << 32;
            readPos |= uint64_t{voice->mPositionFrac.load(std::memory_order_relaxed)} <<
                       (32-FRACTIONBITS);
        }
        std::atomic_thread_fence(std::memory_order_acquire);
    } while(refcount != device->MixCount.load(std::memory_order_relaxed));

    if(voice)
    {
        const ALbufferlistitem *BufferList{Source->queue};
        while(BufferList && BufferList != Current)
        {
            readPos += uint64_t{BufferList->mSampleLen} << 32;
            BufferList = BufferList->mNext.load(std::memory_order_relaxed);
        }
        readPos = minu64(readPos, 0x7fffffffffffffff_u64);
    }

    return static_cast<int64_t>(readPos);
}

/* GetSourceSecOffset
 *